Polycrystalline diamond cutting elements having improved thermal resistance

ABSTRACT

Polycrystalline diamond constructions of this invention have a polycrystalline diamond body and a substrate attached thereto, wherein the diamond body has a material microstructure comprising a plurality of bonded-together diamond crystals forming a polycrystalline matrix phase, and second phase formed from different types of materials or sintering aids designed to reduce or eliminate the amount of free Group VIII elements therein. The use of such materials and the reduction and/or elimination of free Group VIII elements, in addition to graphitization, facilitates the sintering the construction at high pressure/high temperature conditions, e.g., greater than about 65 Kbar, to produce a construction having a high degree of thermal stability and/or thermal resistance when compared to conventional PCD materials. Polycrystalline diamond constructions of this invention are preferably configured as cutting elements that are disposed on drill bits used for drilling subterranean earthen formations.

FIELD OF THE INVENTION

This invention generally relates to cutting elements comprising one or more regions of bonded together diamond crystals and, more specifically, to cutting elements comprising bonded together diamond crystals that are specially engineered to provide an improved degree of thermal resistance during cutting and/or wearing operations when compared to cutting elements that are formed from conventional polycrystalline diamond materials, thereby providing improved service life in desired cutting and/or drilling applications.

BACKGROUND OF THE INVENTION

Polycrystalline diamond (PCD) materials and PCD elements formed therefrom are well known in the art. Conventional PCD is formed by combining synthetic diamond grains with a suitable solvent catalyst material to form a mixture. The mixture is subjected to processing conditions of extremely high pressure/high temperature, where the solvent catalyst material promotes desired intercrystalline diamond-to-diamond bonding between the grains, thereby forming a PCD structure. The resulting PCD structure produces enhanced properties of wear resistance and hardness, making PCD materials extremely useful in aggressive wear and cutting applications where high levels of wear resistance and hardness are desired.

Solvent catalyst materials typically used for forming conventional PCD include metals from Group VIII of the Periodic table, with cobalt (Co) being the most common. Conventional PCD can comprise from 85 to 95 percent by volume diamond and a remaining amount solvent catalyst material. The material microstructure of conventional PCD comprises regions of intercrystalline bonded diamond with solvent catalyst material attached to the diamond and/or disposed within interstices or interstitial regions that exist between the intercrystalline bonded diamond regions.

A problem known to exist with such conventional PCD materials is that they are vulnerable to thermal degradation, when exposed to elevated temperature cutting and/or wear applications, caused by the differential that exists between the thermal expansion characteristics of the interstitial solvent metal catalyst material and the thermal expansion characteristics of the intercrystalline bonded diamond. Such differential thermal expansion is known to occur at temperatures of about 400° C., can cause ruptures to occur in the diamond-to-diamond bonding, and eventually result in the formation of cracks and chips in the PCD structure during wear and/or cutting operations, rendering the PCD structure unsuited for further use.

Another form of thermal degradation known to exist with conventional PCD materials is one that is again related to the presence of the solvent metal catalyst in the interstitial regions and the adherence of the solvent metal catalyst to the diamond crystals. Specifically, the solvent metal catalyst is known to cause an undesired catalyzed phase transformation in diamond (converting it to carbon monoxide, carbon dioxide, or graphite) with increasing temperature, thereby limiting practical use of the PCD material to about 750° C.

Attempts at addressing such unwanted forms of thermal degradation in conventional PCD materials are known in the art. Generally, these attempts have focused developing a PCD body having an improved degree of thermal stability or thermal resistance when compared to the conventional PCD materials discussed above. One known technique of improving the thermal stability of a PCD body is by removing all or a portion of the solvent catalyst material therefrom after it has been formed or sintered.

For example, U.S. Pat. No. 6,544,308 discloses a PCD element having improved wear resistance comprising a diamond matrix body that is integrally bonded to a metallic substrate. While the diamond matrix body is formed using a catalyzing material during high temperature/high pressure processing, the diamond matrix body is subsequently treated to render a region extending from a working surface substantially free of the catalyzing material. This same technique is disclosed in Japanese Published Patent Application 59-219500.

Other attempts at improving the thermal stability or thermal resistance of PCD has been to remove the catalyzing material from not just a distinct region of the diamond body, but removing the catalyst material from the entire diamond body, thereby forming what is sometimes referred to in the art as thermally stable polycrystalline diamond (TSP). While this approach produces an entire diamond that is substantially free of the solvent catalyst material, is it fairly time consuming. Additionally, a problem known to exist with this approach is that the lack of solvent metal catalyst within the diamond body precludes the subsequent attachment of a metallic substrate to the diamond body by solvent catalyst infiltration.

Additionally, such TSP materials have a coefficient of thermal expansion that is sufficiently different from that of conventional substrate materials (such as WC—Co and the like) that are typically infiltrated or otherwise attached to the diamond body. The attachment of such substrates to the diamond body is highly desired to provide a diamond bonded compact that can be readily adapted for use in many desirable applications. However, the difference in thermal expansion characteristics between the TSP body and the substrate, and the poor wettability of the TSP body due to the substantial absence of solvent metal catalyst, makes it very difficult to bond the TSP body to conventionally used substrates. Accordingly, such TSP bodies must be attached or mounted directly to a device for use, i.e., without the presence of an adjoining substrate.

Since such TSP bodies are substantially devoid of a metallic substrate they cannot (e.g., when configured for use as a drill bit cutter) be attached to a drill bit by conventional brazing process. The use of such TSP body in this particular application necessitates that the TSP body itself be mounted to the drill bit by mechanical or interference fit during manufacturing of the drill bit, which is labor intensive, time consuming, and does not provide a most secure method of attachment.

While these above-noted known approaches provide insight into diamond bonded constructions capable of providing some improved degree of thermal stability or thermal resistance when compared to conventional PCD materials, it is believed that further improvements in thermal stability for PCD materials useful for desired cutting and/or wear applications can be obtained according to different approaches that are both capable of minimizing the amount of time and effort necessary to achieve the same, and that permit formation of a PCD compact comprising a desired substrate bonded thereto to facilitate attachment of the compact with a desired application device, e.g., a bit for drilling earthen formations.

It is, therefore, desired that polycrystalline diamond constructions and compacts useful in cutting and/or wear applications be developed that include a diamond bonded body having an improved degree of thermal stability and/or resistance when compared to conventional PCD materials, and that can be engineered to include a substrate material bonded thereto to facilitate formation of a compact to permit attachment of the same to an application device by conventional method such as welding or brazing and the like.

SUMMARY OF THE INVENTION

Polycrystalline diamond constructions can be prepared and/or embodied differently within the scope of this invention. In one example embodiment, the polycrystalline diamond construction has a material microstructure comprising a plurality of bonded-together diamond crystals forming a polycrystalline matrix phase, and an intermetallic compound interposed within a boundary phase between the bonded-together diamond crystals. The intermetallic compound comprises a combination or reaction product of one or more materials selected from Group VIII of the Periodic Table, with Cr, Mn, Ti, Zr, Hf, V, Nb, Mo, W, Ta, and alloys thereof. The intermetallic compound operates to stabilize any solvent metal catalyst from Group VIII of the periodic table such that the resulting polycrystalline diamond construction is substantially free of a material consisting exclusively of a Group VIII element. In an example embodiment, the materials selected from the group consisting of Cr, Mn, Ti, Zr, Hf, V, Nb, Mo, W, Ta, and alloys thereof are a carbide.

Other materials useful for forming the polycrystalline diamond construction include Pd. The polycrystalline diamond construction may further comprise a substrate attached thereto that is formed from formed materials selected from the group consisting of ceramics, metals, cermets, and combinations thereof.

Such example polycrystalline diamond construction can be prepared by the process of graphitizing part or all of a precursor diamond powder used to form the polycrystalline diamond construction. The diamond powder is then sintered in the presence of precursor materials used to form the intermetallic compound under high pressure conditions of greater than about 55 Kbar, and under high temperature conditions to form the polycrystalline diamond construction. Such sintering can take place at pressures greater than about 65 Kbar, and greater than about 70 Kbar. Such sintering can take place at elevated temperatures of from about 1,400 to 1,600° C. The precursor materials can either be present in the form of separate powders or can be present as part of the diamond powder. In the event that the polycrystalline diamond construction includes a substrate, such substrate is also attached thereto, which attachment can take place during or after the sintering step.

In another embodiment, the polycrystalline diamond construction comprises a polycrystalline diamond body including a plurality of bonded-together diamond crystals. The polycrystalline diamond body has a diamond volume content of greater than about 94 percent, and the polycrystalline diamond construction may include a substrate attached to the polycrystalline diamond body.

The polycrystalline diamond construction of this embodiment is prepared by graphitizing part or all of a precursor diamond powder used to form the polycrystalline diamond construction. The graphitized diamond powder is combined with a sintering agent comprising Pd and one or more further material selected from the group consisting of Fe, Co, Ni, to form a diamond powder mixture. The Pd is disposed on a surface of diamond grains in the diamond powder, and the one or more further material is disposed on the Pd. The Pd may comprise from 0.01 to 40 percent by weight of the total sintering agent. If desired, the sintering agent can further include one or more material selected from the group consisting of Sn, P, B, W, and mixtures thereof.

In an example embodiment, the Pd and one or more further materials are distributed homogeneously within the diamond powder mixture. The mixture is then sintered under a high pressure condition of greater than about 55 Kbar and a high temperature condition, and the substrate is attached to the polycrystalline diamond body. The sintering pressures and temperature can be the same as noted above for the first example embodiment.

A further example polycrystalline diamond construction of this invention comprises a polycrystalline diamond body including a plurality of bonded-together diamond crystals, and a substrate attached to the body. The polycrystalline diamond construction is prepared by graphitizing part or all of a precursor diamond powder used to form the polycrystalline diamond body. The graphitized diamond powder is combined with a sintering aid comprising a compound having one or more elements selected from the group consisting of Fe, Co, Ni, Mn, Ti, TiO₂, Si, Alkali earth metals, Alkaline earth metals, rare earth elements, and O. The sintering aid compound is selected from the group consisting of silicates, titanates, and oxides. In a preferred embodiment, the diamond powder and the sintering aid are disposed within a container that is sealed off from the atmosphere. The diamond powder and sintering aid is sintered under high pressure conditions of greater than about 70 Kbar, and under high temperature conditions to form the polycrystalline diamond body. The substrate is attached to the polycrystalline diamond body to the substrate.

In all of the example embodiments, the substrate material may or may not include a Group VIII element from the Periodic table, e.g., the substrate can be substantially free of a Group VIII element of the Periodic table. In the event that the substrate does include a Group VIII element, the polycrystalline diamond construction may include an intermediate layer interposed between the polycrystalline diamond construction and the substrate to provide a desired attachment and to minimize and/or to act as a barrier to minimize and/or eliminate the migration of the Group VIII element from the substrate to the polycrystalline diamond construction.

The polycrystalline diamond constructions of this invention are particularly well suited for use as a wear and/cutting element in a wear and/or cutting device. In a preferred embodiment, the polycrystalline diamond constructions of this invention are configured as cutting elements, forming at least part of a working surface of the cutting element. The cutting elements can be used with a bit for drilling subterranean earthen formations. In one embodiment, the drill bit comprises a body having one or more blades projecting outwardly therefrom, and includes a number of the cutting elements attached to the one or more blades, and wherein the polycrystalline diamond construction forms at least part of a working surface of the cutting element. In another embodiment, the drill bit comprises a number of legs extending away from the body, and a number of cones rotatably attached to the legs, wherein the number of cutting elements is attached to one or more of the cones.

Such polycrystalline diamond constructions of this invention display improved properties of thermal stability and/or thermal resistance when compared to conventional PCD materials, and are engineered to include a substrate material bonded thereto to facilitate attachment of the construction, e.g., when configured as a wear and/or cutting element, by conventional method such as welding or brazing and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will be appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIGS. 1A to 1E are perspective views of different polycrystalline diamond compacts of this invention

FIG. 2 is a perspective side view of an insert, for use in a roller cone or a hammer drill bit, comprising the polycrystalline diamond compact of this invention;

FIG. 3 is a perspective side view of a roller cone drill bit comprising a number of the inserts of FIG. 2;

FIG. 4 is a perspective side view of a percussion or hammer bit comprising a number of inserts of FIG. 3;

FIG. 5 is a schematic perspective side view of a diamond shear cutter comprising the polycrystalline diamond compact of this invention; and

FIG. 6 is a perspective side view of a drag bit comprising a number of the shear cutters of FIG. 5.

DETAILED DESCRIPTION

PCD bodies of this invention are specially engineered having a diamond-bonded body having an improved degree of thermal stability when compared to conventional PCD materials. Such PCD bodies can further include a substrate attached thereto, thereby forming a compact, to facilitate attachment of the compact to a desired cutting or wear device, e.g., a bit for drilling earthen formations, by conventional means such as by welding, or brazing and the like.

In a first example embodiment, PCD bodies of this invention are prepared by subjecting a mixture of synthetic diamond powders of desired size and/or distribution, with a suitable diamond synthesizing catalyst material. Diamond powders useful for forming PCD bodies of this first example embodiment have an average diameter grain size in the range of from submicrometer to about 0.1 mm in size, and more preferably in the range of from about 0.005 mm to 0.08 mm. The diamond powder can contain grains having a mono or multi-modal size distribution. In a preferred embodiment for a particular application, the diamond powder has an average particle grain size of approximately 5 to 30 micrometers. However, it is to be understood that the use of diamond grains having a grain size outside of this range may be useful for certain cutting and/or wear applications. In the event that diamond powders are used having differently sized grains, the diamond grains are mixed together by conventional process, such as by ball or attritor milling for as much time as necessary to ensure good uniform distribution.

Example diamond synthesizing catalyst materials include Group VIII iron metals, or Cr, Mn, Ta or alloys containing them. The catalyst material is present at a ratio of from about 0.01 to about 10 percent by weight relative to the diamond powder. In a preferred embodiment, the diamond powder and/or mixture of the diamond powder and the catalyst material is wholly or partially graphitized, which can occur by subjecting the diamond powder or mixture to a graphite material by coating process or the like, or which can occur by subjecting the diamond powder and/or the mixture of diamond powder and the catalyst material to a high temperature condition, to graphitize a part or whole thereof. In a preferred embodiment, the mixture is at least partially graphitized by heating the diamond powder at a temperature of about 1,400° C. or more in vacuum or a nonoxidizing atmosphere.

In an example embodiment, it is desired that in the range of from about 0.5 to 25 percent by volume of the diamond grains be graphitized, and more preferably less than about 10 percent by volume. The extent of the diamond grains that are graphitized can and will vary depending on a number of factors that include the particular grain size of the diamond powder, the process/sintering conditions, and the end use application for the PCD body.

Alternatively, instead of forming graphite from the diamond grains used to form the PCD body, graphitization is understood to include the process of adding graphite in the form of powder or the like to the diamond grains or powder used for forming the PCD body.

In preparing the first embodiment PCD body, it is further desired that one or more materials selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and the like, and mixtures thereof be added to the diamond powder and catalyst material mixture. Such other materials can be added to the mixture as a raw material before processing, or can be included as part of the diamond powder, e.g., infiltrated or otherwise contained in the diamond grains. In an example embodiment, such materials can be provided during processing from a pressure vessel that is made from such material. In an example embodiment, such additional material is diffused into the diamond powder and catalyst material mixture from a pressure vessel formed from the desired additional material during a high pressure/high temperature (HPHT) sintering process. In an example embodiment, a mixture of graphitized diamond powder and catalyst material is loaded into such a pressure vessel, and the pressure vessel is subjected to HPHT process conditions of about 50 Kbar or more, and about 1,400° C. or more. In a preferred embodiment, the graphitized mixture is sintered at a high pressure of about 70 Kbar or more, and at a high temperature of about 1,600° C. or more using a suitable HPHT device, such as a belt press, a cubic press, a torroid press, or the like.

During such HPHT processing, the diamond powder is sintered and intermetallic compounds, consisting of metals or alloys thereof contained in the raw materials and metals from the reaction vessel, are formed. The resulting sintered PCD body comprises a ratio of about 0.01 to 12 percent by weight of the intermetallic compounds relative to bonded diamond crystals.

In this first example embodiment, synthetic diamond powders including Group VIII iron metals of the Periodic table, or Cr, Mn, Ta or alloys thereof are used as a catalyst in the synthesis of diamond as impurities, or boron-containing synthetic diamond powders including Group VIII iron metals, or Cr, Mn, Ta or alloys thereof can be used as a catalyst in the synthesis of diamond in crystals thereof, as impurities in the powders used as the raw materials for forming the PCD body.

In an example embodiment, synthetic diamond powders containing the specified quantity of the catalyst material as an inclusion are wholly or partially graphitized by heating in the manner noted above prior to sintering. The graphitized powders are filled in a pressure or reactive vessel made from at least one metal selected from a group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and the like, and the contents of the vessel are sintered at a super-high pressure and high temperature, under which diamond is stable, while preventing said metals or alloys thereof from raiding thereinto from outside of the system, e.g., with the use of iron group materials and Cr, Mn, and/or Ta in the raw material.

It was found that where synthetic diamond powders, including metallic impurities therein at a ratio of about 0.01 to 10 percent by weight, were used as the starting raw materials, graphitized diamond was converted to diamond again in the sintering process, thereby providing a sintered diamond body. Using less than about 0.1 percent by weight of the metallic impurities results in a mixture that can be difficult to sinter when it is graphitized, while using more than about 10 percent by weight metallic impurities can produce a sintered diamond body that does not have a desired degree of thermal stability or resistance well suited for use in certain cutting and/or wear applications, e.g., such as a cutting element for use with a drill bit.

As noted above, it may be desired that PCD bodies of this first example embodiment be formed optionally using Boron. Synthetic diamond powders useful for making PCD bodies of this invention may include catalyst metal impurities at a ratio of from about 0.01 to about 3 percent by weight and boron. Boron can be added to form a solid solution at a ratio of about 0.001 to about 1 percent by weight. PCD bodies formed using boron display an electrical conductivity almost equivalent to that of the conventional PCD formed by using cobalt as a catalyst material, are remarkably compact and strong, and further display improved thermal stability or resistance when compared to conventional PCD materials.

PCD bodies of this first example embodiment display improved thermal stability or resistance, despite the presence of a catalyst material, when subjected to operating temperatures of about 1,000° C. The improved thermal stability is believed due partly to the relatively small metal content used in making such first example embodiment PCD bodies, when compared to conventional PCD formed by sintering diamond grains impregnated with cobalt. Further, such improved thermal stability is also believed due to the different characteristics and distribution of the metals used in forming the sintered diamond body.

Specifically, sintered PCD bodies of this first example embodiment appear to have diamond crystalline particles that are very closely joined together, as though the catalyst material existed within the crystalline particles themselves rather than on the grain boundary of the particles, such as that found in conventional PCD where the catalyst metal exists on the boundary surface of the diamond particles in the form of a thin film. In conventional PCD, the presence of cobalt on the boundary surface is a result of the cobalt infiltrating into the gaps between the diamond powder during the sintering process, and acting as the bonding phase.

PCD bodies of the first example embodiment include a small amount of thin film-like-metal on the grain boundary of the diamond. However, the thin film is provided in the form of an intermetallic compound that is formed by the action of the at least one of the materials selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and the like being diffused into the raw materials during the sintering process, and being combined or reacting with the catalyst metal. Thus, the metallic phase in the resulting sintered PCD body is not the catalyst metal, and the contact surface area between the metallic phase (in the form of the intermetallic compound) and the diamond is relatively small.

Thus, the nature of the intermetallic phase (not being exclusively catalyst metal), the manner in which the metallic phase is present and/or distributed in the sintered PCD body, and the relatively small amount of the metallic phase, is believed responsible for making the PCD body more resistant to graphitization during high temperature operations, thereby providing a PCD body having improved thermal stability and thermal resistance when compared to conventional PCD materials.

PCD bodies of this first example embodiment may be better understood with reference to the following example:

EXAMPLE First Example Embodiment PCD Body

Synthetic diamond powders having a mean particle size of approximately 25 micrometers and containing the following metallic impurities were used as the starting material. Sample A: Fe—600 ppm; Ni—79,400 ppm; Cr—4300 ppm; Mn—300 ppm; and Ta—200 ppm. Sample B: Fe—1,600 ppm; Ni—11,900 ppm; Cr—500 ppm; Mn—100 ppm; and Ta—500 ppm. The numerical values provided above for the metallic impurities are measured by using a mass spectrometer. Each of the samples is held in a vacuum furnace at approximately 1,400° C. for one hour. The diamond powders are taken out of the vacuum furnace and then tested for degree of graphitization by X-ray diffraction method. Samples A displayed a partial graphitization of approximately 90 percent by weight, and Sample B displayed a partial graphitization of approximately 50 percent by weight. The graphitized Sample A and B powders are each loaded into respective vessels made of Ta, and then the vessels are sealed hermetically. Subsequently, the vessels are held at a pressure of approximately 50 Kbar and a temperature of 1,400° C. for five minutes in a belt-type super-high pressure apparatus to sinter the powders.

The sintered PCD bodies resulting from the Sample A and B mixtures displayed good abrasion resistance and improved thermal stability and thermal resistance when compared to conventional PCD materials. In particular, the thermal resistance was remarkably improved without reducing the strength of the sintered PCD body, making such PCD bodies well suited for use as cutting and/or wear elements on bits used for drilling subterranean formations.

In a second example embodiment, PCD bodies of this invention are formed by combining diamond powder, having a desired grain size or grain size distribution, with a sintering aid or sintering agent. The diamond powder can be of the same average grain sizes described above for the first example embodiment, and can comprise a mono or multimodal distribution of diamond grain sizes. In a preferred embodiment, the diamond grain size is in the range of from about 0.1 micrometer to about 70 micrometers, and more preferably in the range from about 5 to 30-micrometers. Using diamond grains sized less than about 0.1 micrometers may make providing a coating of the sintering aid thereon difficult, and/or may provide a relatively large diamond surface area that may promote unwanted abnormal diamond growth during sintering, which can reduce the wear resistance of the resulting sintered PCD body. Using diamond grains sized greater than about 70 micrometers may promote unwanted cleavage of the sintered diamond particles, which could reduce the strength of the sintered PCD body.

Sintering aids useful for forming second embodiment PCD bodies of this invention include palladium (Pd) within the range of from about 0.1 to 40 percent by weight, based on the total weight of the sintering aid. Pd is useful for reducing the melting point of the sintering aid, thereby enabling sintering of the PCD body at relatively low temperatures. If less than about 0.1 percent by weight Pd is used, the amount may be ineffective for lowing the melting point of the sintering aid to provide a desired reduction in the sintering temperature. If greater than about 40 percent by weight Pd is used, the melting point of the sintering aid conversely increases, thereby making sintering difficult.

The sintering aid can also include at least one sintering assist agent selected from the group of materials including iron (Fe), cobalt (Co), nickel (Ni), and combinations thereof. In an example embodiment, the sintering aid includes Pd, in the amount described above, with a remainder being at least one sintering assist agent selected from the group including Fe, Co, Ni, and mixtures thereof.

PCD bodies of this second example embodiment can be made by preparing a diamond powder having a desired particle size described above, precipitating or otherwise disposing Pd within the range described above onto the surface of each particle of the diamond powder, and disposing the sintering assist agent including at least one component selected from Fe, Co, Ni, and mixtures thereof within the range of about 4 to 20 percent by volume onto the surface of each particle of the diamond powder, and thus preparing a coated diamond powder.

The sintering aid and sintering assist agent are preferably homogeneously distributed in the sintered diamond particles and do not contain unnecessary components. The sintering aid and assist agent are preferably applied to the diamond grains or diamond powder by spray or deposition process, such as by using chemical vapor deposition (CVD) methods, physical vapor deposition (PVD) methods, atomic level deposition (ALD) methods, solution precipitation methods, or the like. An electroless plating technique can also be used to coat or otherwise apply the sintering aid and/or sintering assist agent onto the diamond grains, as disclosed in Japanese Patent Laying-Open No. 8-225875, which is incorporated herein by reference. It is desired that the method that is used be one that is capable of providing a uniform thickness of the sintering assistant agent to thereby promote improve the sintering property of the powder and the strength of the resulting sintered PCD body.

The so-formed coated diamond powder is loaded into an appropriate pressure or reaction vessel and the vessel is loaded into a device capable of subjecting the vessel contents to HPHT conditions sufficient to cause liquid-phase sintering.

Distributing the sintering aid and sintering assist agent homogeneously along the diamond grains by coating the surface of the diamond grains using any one of the above-described techniques is desired for the purpose of facilitating the sintering process and for improving the material structure and properties of the resulting sintered PCD body. Further, the technique of coating the diamond grains with the sintering aid and/or sintering assist agent improves the ability to not only provide a controlled homogeneous distribution of the sintering aid within the diamond powder mixture, but provide tight controls over the amount of the sintering aid (and/or the materials used to form the sintering aid) that is used. For examples, using ALD, one can control the amount of material that is applied to the surface of a diamond grain to one or two atomic layers if so desired.

Alternatively, PCD bodies of this second example embodiment can be prepared by preparing a diamond powder having a particle size as described above, precipitating or otherwise disposing Pd within the range of about 0.01 to 40 percent by weight onto the surface of each particle of the diamond powder, and then applying a sintering assist agent by appropriate technique disclosed above including at least one component selected from Fe, Co, Ni and combinations thereof within the range of 0.1 to 20 percent by volume onto the surface of each particle of the diamond powder, to thus prepare a coated diamond powder. The coated diamond powder can then be molded in a body, and an additional sintering assist agent including at least one of Pd, Fe, Co, Ni, and combinations thereof can be placed into contact with the powder compact body. The so-formed molded body is then subjected to liquid-phase sintering at HPHT conditions, during which conditions the additional sintering assist agent is infiltrated into the powder compact body.

The process of coating the diamond powder particles is desired for the purpose of providing a greater degree of uniformity over the distribution of the sintering material in the mixture during liquid phase sintering, thereby minimizing or avoiding the presence of unwanted voids and/or pools of the sintering material that may adversely impact the material structure of the sintered PCD body. Further supplementing the sintering aid, the sintering assist agent has been found to further improve uniform infiltration during sintering.

Additionally, by using a diamond powder coated with the above-described sintering agents, uniform melting or infiltration of the sintering assist agent occurs, so that sintering becomes possible under conditions that were otherwise not suitable for sintering, e.g., at a reduced temperature conditions, thereby enabling formation of a PCD body having a high diamond content, and desired properties of thermal resistance, strength, and wear resistance at a reduced sintering temperature.

In this second example embodiment PCD body, any of Pd, Fe, Co and Ni can be used by itself as the sintering assist agent for the diamond powder. However, when the sintering assist agent includes Pd in addition to at least one of Fe, Co and Ni, the melting point of the sintering assist agent is reduced and the sintering property of the diamond powder is remarkably improved.

In an example embodiment, it is desired that the coated diamond powder comprises at least about 4 percent by weight of the sintering assist agent to facilitate the above-noted sintering process that will produce a desired sintered PCD body having above-noted performance properties. It is desired that the amount of the sintering assist agent used for this example embodiment be 20 percent by volume at most, as the resulting wear-resistance of the sintered PCD body in view of the reduced diamond content may not be at a level well suited for certain wear and/or cutting applications.

Similarly, when sintering of the coated diamond powder is to be performed in the presence of the additional sintering assist agent, the amount of the sintering assist agent should preferably be at least about 0.1 percent by volume. If the amount of the sintering assist agent is less than about 0.1 percent by volume, then uniform coating by the sintering assist agent on the surface of the diamond particles becomes difficult, making uniform infiltration of the additional sintering assist agent difficult. If the total sintering assist agent in the sintered body exceeds about 20 percent by volume, the diamond content is reduced, which can produce a sintered PCD body having a degree of wear resistance that may be less than that desired for certain wear and/or cutting applications.

When the sintering assistant agent is to be precipitated onto the surface of the diamond particles by electroless plating, mixing or inclusion of impurities in the sintering assistant agent should be prevented as much as possible, in order to obtain a high diamond content after sintering. Considering the fact that catalytic nuclei having high catalytic action must exist on the surface of the diamond particles in the initial reaction of electroless plating, it is preferred that Pd, exhibiting not only the function of a sintering aid but also a desired catalytic action, be coated first onto the surface of the diamond particles. By providing a coating of a sintering assist agent including at least one of Fe, Co and Ni with Pd serving as catalytic nuclei, a coated diamond particle coated with a sintering assistant agent having a smaller amount or degree of impurity can be obtained.

In an example embodiment, it is desired that the amount of Pd precipitated onto the surface of the diamond particle be at least 10⁻⁴ percent by weight to provide a sufficient electroless plating reaction to facilitate providing a coating of the sintering assist agent thereon. If the amount of precipitated Pd is greater than about 40 percent by weight, then the melting point of the sintering assistant agent will be elevated, potentially degrading the sintering property of the PCD body.

The sintering assist agent can also include at least one material selected from the group including tin (Sn), phosphorous (P), and boron (B), in addition to the iron family metal, wherein the Sn, P and/or B serves to lower the melting point of the sintering assist agent, significantly improving the sintering property of the diamond powder coated by the sintering assist agent.

Further, the sintering assist agent can optionally include metal tungsten. As used herein, the substance referred to as “tungsten” can be metallic tungsten (W) or a tungsten compound such as tungsten carbide (WC) or the like. In an example embodiment, the content of tungsten in the sintered PCD body can be up to about 8 percent by weight, based on the total weight of the sintering assist agent. Tungsten has been found useful in controlling unwanted diamond growth that may occur during the sintering process.

The presence of oxygen (O) or oxide adsorbed at the surface of the diamond powder particles in a raw material for manufacturing a diamond sintered body may contribute to defects in the sintered body. Thus, it is desired that amount of oxygen in PCD bodies formed according to this second example embodiment be controlled, and in an example embodiment comprise oxygen in the range from about 0.005 to 0.08 percent by weight.

As for precipitation of P in addition to the iron family element, a sintering assist agent having a desired P concentration can be precipitated by using a hypophosphite, for example sodium hypophosphite, as a reducing agent in the electroless plating solution, and by adjusting the concentration of the reducing agent in the plating solution, the pH of the plating solution, and the temperature during plating. Similarly, for precipitation of B in addition to the iron family element, a sintering assist agent having a desired B concentration can be precipitated by using a boron hydride compound, such as sodium borohydride, as the reducing agent in the electroless plating solution, and by adjusting the concentration of the reducing agent in the plating solution, the pH of the plating solution, and the temperature during plating.

Sn has a superior absorption property with respect to the surface of the diamond powder particle. Therefore, it can be directly absorbed onto the diamond particle surface from a tin chloride solution, for example. Further, precipitation of Pd serving as the catalytic nucleus after absorption of Sn onto the diamond particle surface as pre-processing for electroless plating (sensitizing activating method), or precipitation of Sn and Pd simultaneously (catalyst accelerating method) is preferable, since it promotes absorption of Pd at the surface of the diamond particles.

If the total content of Sn, P and B in the sintering assist agent is less than about 0.01 percent by weight, then the desired effect of lowering the melting point of the sintering assistant agent may not be achieved. By contrast, if the total content of Sn, P and B exceeds about 30 percent by weight, then melting of diamond to the iron family metal which serves as a solvent metal in the sintering assist agent at the time of sintering is hindered, so that the binding strength between diamond particles becomes lower, thus degrading the strength and the thermal properties of the resulting sintered PCD body. In an example embodiment, the total content of Sn, P and B in the sintering assist agent is preferably within the range of about 0.01 to 11.5 percent by weight.

When the diamond particles are to be coated with the sintering assist agent by electroless plating, the iron family element precipitated by electroless plating is, in most cases, precipitated as an oxide. If sintering is performed using a sintering assist agent including an oxide, oxygen derived from the oxide may possibly generate voids in the sintered body, and it may hinder the melting and precipitation reaction of diamond in the sintering assistant agent serving as the solvent. Therefore, it may degrade the property of the diamond sintered body. In order to prevent such an undesirable effect caused by oxygen, the coated diamond powder after electroless plating should preferably be reduced by heat treatment in a vacuum or in a hydrogen atmosphere.

When electroless plating is performed on the diamond powder, the diamond powder can be coated uniformly by the sintering assist agent if the plating solution including the diamond powder is fluctuated or agitated by at least one of stirring and ultrasonic vibration. Further, in order to obtain a diamond sintered body having higher density, it may be desired to develop a graphite coating on the diamond particles, which graphite coating can be provided in the manner described above for the first example embodiment PCD body. In an example embodiment, the graphite coating is formed by heating the diamond powder at high temperature conditions under which the diamond is unstable so that at least a surface portion thereof is converted into graphite. The partially graphitized diamond particles are then coated with the sintering assist agent as described above and the coated particles are thereafter sintered. Alternatively, the diamond particles can be coated with the sintering assist agent and then the coated particles can be at least partially graphitized, and thereafter the coated graphitized particles can be sintered.

Graphitizing at least a portion of the diamond particle surface is desired because the diamond powder itself is not susceptible to plastic deformation, even under high pressure, causing spaces that tend to remain between diamond particles. However, graphite is susceptible to plastic deformation, and the surface portion that is graphitized can plastically deform under pressure, causing the density of the sintered body to be substantially improved. Further, considering melting of carbon and re-precipitation thereof in the sintering assist agent during sintering, the speed of reaction of graphite is faster than that of diamond, and hence the sintering property is improved if the diamond surface is turned into graphite.

For these reasons, it is believed that at least partially graphitizing the diamond particles operates to produce a sintered PCD body having a diamond density that is higher than can otherwise be achieved without graphitization. In an example embodiment, it is desired that the ratio of graphitization of the diamond particles be in the range of from about 0.5 percent by volume to about 25 percent by volume, and preferably less than about 10 percent by volume.

It is possible that various other materials can be included in the sintered PCD body in small quantities. For example, the coated diamond powder is generally filled into a vessel formed of a cemented carbide or a refractory metal and then sintered. Therefore, one or more materials selected from the group consisting of W, Ta, Mo, and Cr, which are the components of the vessel, or carbides thereof, may possibly be mixed into and present in the sintered body. However, in the event that such additional materials are mixed into the sintered body, it is desired that the diamond content in the sintered PCD body be within the range of about 80 to 96 percent by volume.

Similarly, even when the additional sintering assist agent is brought into contact with the powder compact body to supplement the sintering assist agent in the coated diamond powder, and infiltrated into the powder compact body during sintering, it is desired that the diamond content of the sintered body be within the range of about 80 to 96 percent by volume. The additional sintering assist agent arranged in contact with such powder compact body may have similar compositions as those for the sintering assist agent used for coating of the diamond particle.

PCD bodies formed according to the second example embodiment of this invention can be better understood with reference to the following Examples.

EXAMPLE Second Example Embodiment PCD Body

Diamond powder having an average grain size of approximately 0.1 to 4 micrometers is selected and two different samples (Samples A and B) are prepared by coating the powder with different volume percentages of the sintering assist agent. For both samples, the sintering assist agent is applied by electroless plating technique and the diamond powder is prepared in the following manner. First, the diamond powder is degreased in alcohol. The degreased diamond powder is cleaned in flowing water, cleaned in a hydrochloric acid solution of approximately five percent by weight, and then again cleaned in flowing water. The diamond powder thus cleaned is immersed for one minute in a solution including stannous chloride and hydrochloric acid at room temperature as pre-processing, so as to cause absorption of Sn at the surface of the diamond particles (sensitizing). The sensitized diamond powder is washed with water and thereafter immersed for one minute in a hydrochloric acid solution containing palladium chloride at room temperature, and thus Pd is precipitated at the surface of the diamond particles (activated).

The activated diamond powder is washed with water, and thereafter immersed for a prescribed time period in a Co—Fe—P electroless plating solution held at approximately 75° C., containing cobalt sulfate, iron sulfate and sodium hypophosphite. The longer the time of immersion in the electroless plating solution, the larger the amount of sintering assist agent coated onto the surface of the diamond particles, and the larger the content of the sintering assist agent in the powder samples. In the step of electroless plating, the preplating solution and plating solution are stirred and at the same time subjected to ultrasonic vibration. The coated diamond powder which is subjected to electroless plating in this manner is cleaned, the surface of the diamond particles is partially graphitized by heat treatment in a vacuum at approximately 1,000° C. for 60 minutes, and then the powder is collected, whereby the coated powder Samples A and B have the following contents and compositions of the sintering assist agent:

Sample A—Total content of the sintering assist agent is approximately 6 percent by volume; sintering assist agent composition comprised approximately 92.9 percent by weight Co, 0.05 percent by weight Pd, 3.95 percent by weight Fe, 3 percent by weight P, and 0.1 percent by weight Sn.

Sample B—Total content of the sintering assist agent is approximately 13 percent by volume; sintering assistant agent composition comprised approximately 92.9 percent by weight Co, 0.05 percent by weight Pd, 3.95 percent by weight Fe, 3 percent by weight P, and 0.1 percent by weight Sn.

It is to be understood that the following two examples are provided for purposes of reference and that other samples of second embodiment PCD bodies comprising different types and/or amounts of the sintering assists agents, different sizes of diamond powder, and using different techniques for coating or applying the sintering assist agents are within the scope of this invention. Other coating techniques may include arc ion plating methods, ball milling by including the powder component and using a container and balls formed from Teflon, and ball milling using mixing balls and/or the container formed from a desired coating material, e.g., cemented tungsten carbide (WC—Co).

The Sample A and B coated diamond powders are each sealed in a container or vessel formed of tantalum and exposed to a HPHT condition of approximately 50 Kbar and a temperature of approximately 1,400° C. for 10 minutes by using a belt-type high pressure apparatus. The sintered PCD bodies formed from Samples A and B demonstrated a high degree of wear resistance and strength even though the amount of sintering assistant agent was relatively small, thus making such PCD bodies well suited for use as cutting and/or wear elements in such applications as bits used to drill earthen formations.

Third example embodiment PCD bodies of this invention comprise approximately 0.1 to 30 percent by volume of a compound containing at least one metal selected from the group consisting of Fe, Co, Ni, Mn, Ti and O, and the balance of diamond. In one example embodiment, the compound containing at least one metal selected from the group consisting of Fe, Co, Ni, Mn, Ti, and O is a titanate of a metal selected from the group consisting of Fe, Co, Ni, and Mn. In another example embodiment, the compound containing at least one metal selected from the group consisting of Fe, Co, Ni, Mn, Ti, and O is a composite oxide or solid solution consisting of an oxide of a metal selected from the group consisting of Fe, Co, Ni, Mn, and titanium oxide (TiO₂).

Diamond powder useful for forming third example embodiment PCD bodies of this invention can be the same as that disclosed above for the first and second example embodiment PCD bodies of this invention. In place of, or in addition to, using diamond, non-diamond carbons such as graphite, glassy carbons, pyrolytic graphites, and the like can be used as the raw material.

Example titanates can include FeTiO₃, FeTi₂O₅, CoTiO₃, MnTiO₃, NiTiO, and the like. Such materials are capable of exhibiting a strong catalytic function for diamond and when used as a sintering agent, promote formation of a strongly-bonded matrix of diamond grains. In a preferred embodiment, such sintering agent has a grain diameter of from about 0.01 to 10 micrometers. Such sintering aids are stable at a high temperature, e.g. about 1,300° C., providing a PCD body having improved thermal resistance when compared to conventional PCD materials.

Such third embodiment PCD bodies can be made by preparing a mixture of diamond powder or non-diamond carbon powder with a titanate of Fe, Co or a mixture of iron oxide or cobalt oxide and titanium oxide under HPHT conditions that are in the thermodynamically stable region of diamond. The diamond and sintering agent can be mechanically mixed by dry or wet process and the resulting powder can be compressed and molded or charged in a capsule of Mo or the like, followed by sintering at a HPHT conditions.

Other third example embodiment PCD bodies of this invention comprise approximately 0.1 to 30 percent by volume of a compound containing Ti, at least one metal selected from the group consisting of alkali metals and alkaline earth metals, and oxygen, and the balance diamond. In one such embodiment, the compound containing titanium, at least one metal selected from the group consisting of alkali metals and alkaline earth metals, and oxygen is a titanate of a metal selected from the group consisting of alkali metals and alkaline earth metals. In another such embodiment, the compound containing titanium, at least one metal selected from the group consisting of alkali metals and alkaline earth metals, and oxygen is a composite oxide or solid solution consisting of an oxide of a metal selected from the group consisting of alkali metals and alkaline earth metals and titanium oxide.

Example titanates of an alkali metal or alkaline earth metal include LiTiO₃, MgTiO₃, CaTiO₃, SrTiO₃, or the like. Sintering agents comprising titanates of alkali metals or alkaline earth metals, or composite oxides or solid solutions of alkali metal oxides or alkaline earth metal oxides with titanium oxides are desired as these materials are stable at a high temperature, e.g. about 1,500° C., contributing improved thermal resistance to the PCD body when compared to conventional PCD materials. PCD bodies formed from such sintering aids are made in the same manner as described above for the third example embodiment PCD body.

Still other third example embodiment PCD bodies of this invention comprise approximately 0.1 to 30 percent by volume of a compound containing a rare earth element, titanium and oxygen, and the balance of diamond. In an example embodiment, the compound containing a rare earth element, titanium and oxygen is a titanate of a rare earth element. In another embodiment, the compound containing a rare earth element, titanium and oxygen is a composite oxide or solid solution consisting of an oxide of a rare earth element and titanium oxide.

Example titanates of a rare earth element include M₂TiO₅ or M₂Ti₂O₇, wherein M is a rare earth element. The rare earth element can include scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), prometium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Example oxides of a rare earth element include M₂O₃ or MO₂, wherein M is a rare earth element. Such sintering aids are stable at a high temperature, e.g. about 1,300° C., thereby providing improved thermal resistance to the sintered PCD body when compared to conventional PCD.

Still other third example embodiment PCD bodies of this invention comprise approximately 0.1 to 30 percent by volume of a compound containing an alkaline earth metal, silicon and oxygen, and the balance of diamond. In an example embodiment, the compound containing an alkaline earth metal, silicon and oxygen is a silicate of an alkaline earth metal. In another example embodiment, the compound containing an alkaline earth metal, silicon and oxygen is a composite oxide or solid solution consisting of an oxide of an alkaline earth metal and silicon oxide.

Example silicates of an alkaline earth metal include MgSiO₃, Mg₂SiO₄, Mg₂Si₃O₄, CaSiO₃, Ca₂SiO₄, BaSi₂O₅, Ba₂Si₃O₈, or the like. Such sintering aids are stable at a high temperature, e.g. about 1,300° C., thereby providing improved thermal resistance to the sintered PCD body when compared to conventional PCD.

Still other third example embodiment PCD bodies of this invention comprise approximately 0.1 to 30 percent by volume of a compound containing a rare earth element, silicon and oxygen, and the balance of diamond. In an example embodiment, the compound containing a rare earth element, silicon and oxygen is a silicate of a rare earth element. In another example embodiment, the compound containing a rare earth element, silicon and oxygen is a composite oxide or solid solution consisting of an oxide of a rare earth element and silicon oxide.

Example silicates of a rare earth element include, for example, M₂SiO₅ or M₂Si₂O₇, wherein M is a rare earth element. The rare earth element can include scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), prometium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu). Example oxides of a rare earth element include M₂O₃ or MO₂, wherein M is a rare earth element. Such sintering aids are stable at a high temperature, e.g. about 1,400° C., thereby providing improved thermal resistance to the sintered PCD body when compared to conventional PCD.

Still other third example embodiment PCD bodies of this invention comprise approximately 0.1 to 30 percent by volume of a compound containing silicon, titanium and oxygen, and the balance of diamond. In example embodiment, the compound containing silicon, titanium and oxygen is a composite oxide or solid solution consisting of silicon oxide (SiO₂) and titanium oxide (TiO₂). In such example embodiment, the mixture of silicone oxide and titanium oxide comprises 0.1 to 50 percent by volume titanium oxide.

In an example embodiment, the silicon oxide used in the mixture of silicon oxide and titanium oxide is silicic acid, or silicon oxide hydrate. Suitable silicic acids include H₄SiO₄, H₂SiO₃, H₂Si₂O₂, and the like, and suitable silicon oxide hydrates include SiO₂—H₂O. Such sintering aids are stable at a high temperature, e.g. about 1,500° C., thereby providing improved thermal resistance to the sintered PCD body when compared to conventional PCD.

PCD bodies, constructed in accordance with principles of this invention have a diamond volume content greater than about 94 percent, and preferably greater than about 96 percent. Such PCD bodies can be used to form cutting and/or wear elements for use with desired cutting and/or devices to address certain cutting and/or wear applications. In an example embodiment, such PCD bodies and can be further combined with a substrate to form a PCD construction useful in desired cutting and/or wear applications. The ability to combine such PCD bodies with a substrate is desired for certain cutting and/or wear applications to facilitate attachment of the so-formed PCD construction to the desired cutting or wear device. For example, when the PCD body is designed for use as a cutting and/or wear element for attachment with a bit, i.e., a drill bit used for drilling subterranean earthen formations, it is desired that such cutting and/or wear element include a substrate that can be attached by conventional technique, such as brazing or welding or the like, to the bit body.

Substrates useful for forming PCD compacts having PCD bodies of this invention include those selected from the group of materials including ceramic materials, metallic materials, and cermet materials. Suitable substrates can include those conventionally used to form PCD compacts, such as those formed from metallic and cermet materials such as WC—Co. When the substrate material is one that includes a metal solvent catalyst, i.e., a Group VIII element of the Periodic table that is capable of infiltrating into the PCD body during HPHT processing and catalyzing the formation of diamond-to-diamond bonds during sintering conditions, then it is desired that such substrate be attached to the PCD body in a manner that avoids such infiltration.

Accordingly, substrate materials including a solvent metal catalyst can be attached to the PCD body by welding, brazing, or other process that avoids infiltration of the solvent metal catalyst into the PCD body. Alternatively, such substrates can be attached to the PCD body during the HPHT process used to form the sintered PCD body, or during a subsequent HPHT process, by using an intermediate layer interposed between the PCD body and the substrate. In such case, the intermediate layer is one formed from a material that is substantially free of a Group VIII element and that both facilitates attachment of the substrate indirectly to the PCD body, and that acts as a barrier to prevent unwanted infiltration of the solvent metal catalyst from the substrate into the PCD body.

Example intermediate layer materials include those that are carbide formers, e.g., that react with the carbon in the diamond body to form a carbide. Suitable carbide forming materials include refractory metals such as those selected from Groups IV through VII of the Periodic table. Example refractory materials include Ti, Ta, W, Mo, Zr and the like.

Other materials useful for forming the intermediate layer include ceramic materials such as TiC, Al₂O₃, Si₃N₄, SiC, SiAlON, TiN, ZrO₂, WC, TiB₂, AlN and SiO₂, also Ti_(X)AlM_(Y) (where x is between 2-3, M is carbon or nitrogen or a combination of these, and y is between 1-2). Like the carbide forming materials, the ceramic material that is selected is one that is capable of forming a bond between the PCD body and substrate by HPHT process without itself infiltrating or causing unwanted infiltration of materials present in the substrate into the PCD body during the HPHT process.

Still other materials useful for forming the intermediate layer can include non-carbide forming materials such as non-refractory metals and high-strength braze alloys. A desired characteristic of such non-refractory metals and high-strength braze alloys is that they be capable of infiltrating into one or both of the PCD body and substrate during HPHT conditions, and are non-catalytic with respect to the diamond in the PCD body. Suitable non-refractory metals and high-strength braze alloys include copper, Ni—Cr alloys, and brazes containing high percentages of elements such as palladium and similar high strength materials, and Cn-based active brazes. A particularly preferred non-refractory metal useful as an intermediate material is copper due to its relatively low melting temperature, below that of cobalt, and its ability to form a bond of sufficient strength with the PCD body. The ability to provide an intermediate material having a relatively low melting temperature is desired for the purpose of avoiding potential infiltration of any solvent metal catalyst from the substrate into the PCD body.

Such intermediate material can be provided in the form of a preformed layer, e.g., in the form of a foil or the like. Alternatively, the intermediate material can be provided in the form of a green-state part, or can be provided in the form of a coating that is applied to one or both of the interface surfaces of the PCD body and the substrate. It is to be understood that one or more intermediate layers can be used to achieve the desired bonding and/or barrier and or mechanical properties between the PCD body and the substrate.

It is to be understood that substrates comprising a catalyst material can be attached to the PCD body using the intermediate layer at pressure and/or temperature conditions that are below the HPHT conditions used to sinter the PCD body, e.g., they can be attached after the PCD body has been sintered by using less extreme pressure and/or temperature conditions.

Alternatively, substrates useful for forming compacts comprising PCD bodies of this invention can be formed from materials that do not include a solvent metal catalyst material, such as the Group VIII elements conventionally used to form PCD like Co. Examples of such materials include carbides, nitrides, borides, and carbonitrides or the like, that include a material, e.g., a carbide former, that is capable of forming an attachment bond with the PCD body without acting as a catalyst material. Such attachment can be achieved during HPHT sintering of the PCD body, or can be achieved by subjecting the already-formed PCD body and substrate to a temperature and/or pressure condition less extreme than the one used to form the sintered PCD body. An example of such substrate material is tungsten carbide molybdenum (WC—Mo).

Accordingly, PCD bodies of this invention can be used to form PCD construction through the use of: (1) a substrate material comprising a solvent catalyst material by welding, brazing, or other technique that does not result in infiltration of the catalyst material into the PCD body, (2) a substrate material comprising a catalyst material and that is attached to the PCD body via an intermediate layer of material that both facilitates attachment between the PCD body and substrate while also acting as a barrier to prevent the catalyst material in the substrate from infiltrating into the PCD body; and (3) a substrate material that does not include a solvent catalyst material, but that includes a material capable of forming an attachment with the PCD body.

FIG. 1A illustrates an example PCD construction 16 formed in accordance with this invention. The PCD construction 16 generally comprises a PCD body 18, formed from the materials and in the manner described above, that is attached to a desired substrate 20. Although the PCD construction 16 is illustrated as being generally cylindrical in shape and having a disk-shaped flat or planar surface 22, it is understood that this is but one preferred embodiment and that the PCD construction can be configured other than as specifically disclosed or illustrated. It is further to be understood that the construction or compact 16 may be configured having working or cutting surfaces disposed along the disk-shaped surface 22 and/or along side surfaces 24 and/or along a beveled surface interposed therebetween of the PCD body, depending on the particular cutting or wear application. Alternatively, the PCD compact may be configured having an altogether different shape but generally comprising a substrate and a PCD body attached to the substrate, wherein the PCD body is provided with working or cutting surfaces oriented as necessary to perform working or cutting service when the compact is mounted to a desired drilling or cutting device, e.g., a drill bit.

FIGS. 1B to 1D illustrate alternative embodiments of PCD constructions having a substrate and/or PCD body configured differently than that illustrated in FIG. 1A. For example, FIG. 1B illustrates a PCD compact 16 configured in the shape of a preflat or gage trimmer including a cut-off portion 19 of the PCD body 18 and the substrate 20. The preflat includes working or cutting surface positioned along a disk-shaped surface 22 and a side surface 24 working surface. Alternative preflat or gage trimmer PCD compact configurations intended to be within the scope of this invention include those described in U.S. Pat. No. 6,604,588, which is incorporated herein by reference.

FIG. 1C illustrates another embodiment of a PCD compact 16 of this invention configured having the PCD body 18 disposed onto an angled underlying surface of the substrate 20 and having a disk-shaped surface 22 that is the working surface and that is positioned at an angle relative to an axis of the compact. FIG. 1D illustrates another embodiment of a PCD compact 16 of this invention configured having the substrate 20 and the PCD body 18 disposed onto a surface of the substrate. In this particular embodiment, the PCD body has a domed or convex surface 22 serving as the working surface 22.

FIG. 1E illustrates a still other embodiment of a PCD construction 16 that is somewhat similar to that illustrated in FIG. 1A in that it includes a PCD body 18 disposed on the substrate 20 and having a disk-shaped surface 22 as a working surface. Unlike the embodiment of FIG. 1A, however, this PCD compact includes an interface 21 between the PCD body and the substrate that is not uniformly planar. In this particular example, the interface 21 is canted or otherwise non-axially symmetric. It is to be understood that PCD compacts of this invention can be configured having PCD body-substrate interfaces that are uniformly planer or that are not uniformly planer in a manner that is symmetric or nonsymmetric relative to an axis running through the compact. Examples of other configurations of PCD compacts having nonplanar PCD body-substrate interfaces include those described in U.S. Pat. No. 6,550,556, which is incorporated herein by reference.

A feature of PCD bodies and/or constructions or compacts formed therefrom of this invention is that they display an improved degree of thermal stability and/or thermal resistance when compared to conventional PCD, e.g., PCD made by only using diamond powder and a solvent metal catalyst, while at the same time providing a desired degree of strength and toughness unique to conventional PCD.

A still further feature is the ability to achieve such improved thermal stability and/or resistance while at the same time being able to provide a compact construction comprising a substrate. This facilitates attaching the compact to different types of well known cutting and wear devices such as drill bits and the like by conventional attachment techniques, such as by brazing, welding, or the like.

PCD bodies and constructions of this invention can be used in a number of different applications, such as tools for mining, cutting, machining and construction applications, where the combined properties of thermal stability, wear and abrasion resistance, and strength and toughness are highly desired. PCD bodies and compacts of this invention are particularly well suited for forming working, wear and/or cutting components in machine tools and drill and mining bits such as roller cone rock bits, percussion or hammer bits, diamond bits, and shear cutters.

FIG. 2 illustrates an embodiment of a PCD construction of this invention provided in the form of an insert 62 used in a wear or cutting application in a roller cone drill bit or percussion or hammer drill bit. For example, such PCD inserts 62 are constructed having a substrate portion 64, formed from one or more of the substrate materials disclosed above, that is attached to a PCD body 66 formed from the materials and in the manner described above. In this particular embodiment, the insert PCD body comprises a domed working surface 68. The insert 62 can be pressed or machined into the desired shape or configuration. It is to be understood that PCD bodies and/or compacts can be used with inserts having geometries other than that specifically described above and illustrated in FIG. 2.

FIG. 3 illustrates a rotary or roller cone drill bit in the form of a rock bit 70 comprising a number of the wear or cutting PCD inserts 72 disclosed above and illustrated in FIG. 2. The rock bit 70 comprises a body 74 having three legs 76 extending therefrom, and a roller cutter cone 78 mounted on a lower end of each leg. The inserts 72 are the same as those described above comprising the PCD bodies and/or compacts described above, and are provided in the surfaces of each cutter cone 78 for bearing on a rock formation being drilled.

FIG. 4 illustrates the PCD insert described above and illustrated in FIG. 2 as used with a percussion or hammer bit 80. The hammer bit generally comprises a hollow steel body 82 having a threaded pin 84 on an end of the body for assembling the bit onto a drill string (not shown) for drilling oil wells and the like. A plurality of the inserts 86 is provided in the surface of a head 88 of the body 82 for bearing on the subterranean formation being drilled.

FIG. 5 illustrates a PCD compact constructed as described above embodied in the form of a shear cutter 90 used, for example, with a drag bit for drilling subterranean formations. The PCD shear cutter comprises a PCD body 92 attached to a cutter substrate 94 as described above. The PCD body 92 includes a working or cutting surface 96 that can include top, side, and/or beveled surfaces. It is to be understood that PCD compacts can be configured as shear cutters having geometries other than that specifically described above and illustrated in FIG. 5.

FIG. 6 illustrates a drag bit 98 comprising a plurality of the PCD shear cutters 100 described above and illustrated in FIG. 5. The shear cutters are each attached to blades 102 that extend from a head 104 of the drag bit for cutting against the subterranean formation being drilled. Because the PCD shear cutters of this invention include a metallic substrate, they are attached to the blades by conventional method, such as by brazing, welding or the like.

Other modifications and variations of PCD bodies and constructions comprising the same as practiced according to the principles of this invention will be apparent to those skilled in the art. It is, therefore, to be understood that within the scope of the appended claims, this invention may be practiced otherwise than as specifically described. 

1. An earth boring drill bit comprising: a body having a number of cutting elements attached thereto, wherein one or more of the cutting elements includes a polycrystalline diamond construction having a material microstructure comprising: a plurality of bonded-together diamond crystals forming a polycrystalline matrix phase, and an intermetallic compound interposed within a boundary phase between the bonded-together diamond crystals, wherein the intermetallic compound comprises a combination or reaction product of one or more materials selected from Group VIII of the Periodic Table, with Cr, Mn, Ti, Zr, Hf, V, Nb, Mo, W, Ta, and alloys thereof; and a substrate attached to the polycrystalline diamond construction, and wherein the substrate is formed from a material selected from the group consisting of ceramics, metals, cermets, and combinations thereof; wherein the polycrystalline diamond construction is prepared by the process of: graphitizing part or all of a precursor diamond powder used to form the polycrystalline diamond construction, sintering the diamond powder in the presence of precursor materials used to form the intermetallic compound under high pressure conditions of greater than about 55 Kbar, and under high temperature conditions to form the polycrystalline diamond construction; and attaching the polycrystalline diamond construction to the substrate.
 2. The drill bit as recited in claim 1 wherein the body includes one or more blades projecting outwardly therefrom, and the number of cutting elements are attached to the one or more blades, and wherein the polycrystalline diamond construction forms at least part of a working surface of the cutting element.
 3. The drill bit as recited in claim 1 further comprising a number of legs extending away from the body, and a number of cones rotatably attached to the legs, wherein the number of cutting elements are attached to one or more of the cones, and wherein the polycrystalline diamond construction forms at least part of a working surface of the cutting element.
 4. The drill bit as recited in claim 1 wherein the polycrystalline diamond construction further comprises Pd.
 5. The drill bit as recited in claim 4 wherein the Pd is disposed on a surface of diamond grains in the diamond powder before the step of sintering.
 6. The drill bit as recited in claim 5 wherein the precursor material used to form the intermetallic compound is disposed on a surface of the Pd layer disposed on the diamond grains.
 7. The drill bit as recited in claim 1 wherein the substrate comprises a Group VIII element from the Periodic table, and an intermediate layer is interposed between the polycrystalline diamond construction and the substrate, and wherein the intermediate layer is formed from a material that is substantially free of a Group VIII element of the Periodic table.
 8. The drill bit as recited in claim 1 wherein the substrate is formed from a cermet material that is substantially free of a Group VIII element of the Periodic table.
 9. The drill bit as recited in claim 1 wherein the intermetallic compound comprises a carbide of the materials selected from the group consisting of Cr, Mn, Ti, Zr, Hf, V, Nb, Mo, W, Ta, and alloys thereof.
 10. The drill bit as recited in claim 1 wherein the step of sintering the polycrystalline diamond construction takes place at a pressure of greater than about 65 Kbar.
 11. The drill bit as recited in claim 1 wherein the step of sintering the polycrystalline diamond construction takes place at a pressure of greater than about 70 Kbar.
 12. The drill bit as recited in claim 1 wherein the step of sintering the polycrystalline diamond construction takes place at a temperature of from about 1,400 to 1,600 C.
 13. The drill bit as recited in claim 1 wherein during the step of graphitizing, less than about 10 percent by volume of diamond grains in the diamond powder are graphitized.
 14. The drill bit as recited in claim 1 wherein during the step of graphitization, less than about 5 atomic layers of graphite are formed on diamond grains in the diamond powder.
 15. The drill bit as recited in claim 1 wherein one or more of the materials selected from the group consisting of Cr, Mn, Ti, Zr, Hf, V, Nb, Mo, W, Ta, and alloys thereof is present within the diamond grains before sintering.
 16. The drill bit as recited in claim 1 wherein one or more of the materials selected from the group consisting of Cr, Mn, Ti, Zr, Hf, V, Nb, Mo, W, Ta, and alloys thereof is added to the diamond grains to form a diamond mixture before sintering.
 17. The drill bit as recited in claim 1 wherein the materials used to make the intermetallic compound comprises in the range of 0.01 to 10 percent by weight Cr, Mn, Ti, Zr, Hf, V, Nb, Mo, W, Ta, and alloys thereof.
 18. The drill bit as recited in claim 1 wherein before the step of sintering, the diamond powder is disposed within a container that is sealed off from the atmosphere.
 19. The drill bit as recited in claim 1 wherein the polycrystalline diamond construction has a diamond volume content of greater than about 94 percent.
 20. The drill bit as recited in claim 1 wherein the polycrystalline diamond construction is substantially free of a material consisting exclusively of a Group VIII element of the Periodic table.
 21. A polycrystalline diamond construction comprising: a polycrystalline diamond body having a material microstructure comprising a plurality of bonded-together diamond crystals forming a polycrystalline matrix phase, and an intermetallic compound interposed within a boundary phase between the bonded-together diamond crystals, wherein the intermetallic compound comprises a combination or reaction product of one or more materials selected from Group VIII of the Periodic Table, with Cr, Mn, Ti, Zr, Hf, V, Nb, Mo, W, Ta, and alloys thereof, wherein the polycrystalline diamond body is substantially free of a material consisting exclusively of a Group VIII element of the Periodic table; and a substrate attached to the polycrystalline diamond construction, wherein the substrate is formed from a material selected from the group consisting of ceramics, metals, cermets, and combinations thereof that are substantially free of a Group VIII element of the Periodic table; wherein the polycrystalline diamond construction is prepared by the process of: placing the diamond powder within a container that is sealed off from the atmosphere; sintering the diamond powder in the presence of the materials used to form the intermetallic compound under high pressure conditions of greater than about 55 Kbar, and under high temperature conditions to form the polycrystalline diamond construction, wherein some or all of the materials used to form the intermetallic compound is present in the diamond grains forming the diamond powder; and attaching the polycrystalline diamond construction to the substrate.
 22. The polycrystalline diamond construction as recited in claim 21 wherein the intermetallic compound is a carbide.
 23. The polycrystalline diamond construction as recited in claim 22 wherein the materials used to make the intermetallic compound comprises in the range of 0.01 to 10 percent by weight Cr, Mn, Ti, Zr, Hf, V, Nb, Mo, W, Ta, and alloys thereof.
 24. The polycrystalline diamond construction as recited in claim 21 wherein the process of preparing further comprises graphitizing part or all of a precursor diamond powder used to form the polycrystalline diamond body.
 25. A polycrystalline diamond construction comprising: a polycrystalline diamond body having a material microstructure comprising a plurality of bonded-together diamond crystals forming a polycrystalline matrix phase, and an intermetallic compound interposed within a boundary phase between the bonded-together diamond crystals, wherein the intermetallic compound comprises a combination or reaction product of one or more materials selected from Group VIII of the Periodic Table, with Cr, Mn, Ti, Zr, Hf, V, Nb, Mo, W, Ta, and alloys thereof, wherein the polycrystalline diamond body is substantially free of a material consisting exclusively of a Group VIII element of the Periodic table, and has a diamond volume content of greater than about 96 percent; and a substrate attached to the polycrystalline diamond construction, wherein the substrate is formed from a material selected from the group consisting of ceramics, metals, cermets, and combinations thereof; wherein the polycrystalline diamond construction comprises a diamond content of about 96 percent by volume or more and is prepared by the process of: graphitizing part or all of a precursor diamond powder used to form the polycrystalline diamond body; placing the diamond powder within a container that is sealed off from the atmosphere; sintering the diamond powder in the presence of the materials used to form the intermetallic compound under high pressure conditions of greater than about 55 Kbar, and under high temperature conditions to form the polycrystalline diamond construction, wherein the materials used to form the intermetallic compound are combined with the diamond powder to form a mixture prior to sintering; and attaching the polycrystalline diamond construction to the substrate.
 26. The polycrystalline diamond construction as recited in claim 25 wherein the intermetallic compound is a carbide.
 27. The polycrystalline diamond construction as recited in claim 26 wherein the materials used to make the intermetallic compound comprises in the range of 0.01 to 10 percent by weight Cr, Mn, Ti, Zr, Hf, V, Nb, Mo, W, Ta, and alloys thereof.
 28. An earth boring drill bit comprising: a body and a number of cutting elements attached thereto, one or more of the cutting elements comprising a polycrystalline diamond construction that is formed from a plurality of bonded-together diamond crystals, wherein the polycrystalline diamond construction comprises: a polycrystalline diamond body having a diamond volume content of greater than about 94 percent; and a substrate attached to the polycrystalline diamond body, wherein the substrate is formed from a material selected from the group consisting of ceramics, metals, cermets, and combinations thereof; wherein the polycrystalline diamond construction is prepared by the process of: graphitizing part or all of a precursor diamond powder used to form the polycrystalline diamond construction; combining the graphitized diamond powder with a sintering agent comprising Pd and one or more further material selected from the group consisting of Fe, Co, Ni, to form a diamond powder mixture, wherein the Pd is disposed on a surface of diamond grains in the diamond powder and the one or more further material is disposed on the Pd, and wherein the Pd and one or more further materials are distributed homogeneously within the diamond powder mixture; sintering the diamond powder mixture under a high pressure condition of greater than about 55 Kbar and a high temperature condition; and attaching the diamond body to the substrate to form the polycrystalline diamond construction.
 29. The drill bit as recited in claim 28 wherein the body includes one or more blades projecting outwardly therefrom, and the number of cutting elements are attached to the one or more blades, and wherein the polycrystalline diamond construction forms at least part of a working surface of the cutting element.
 30. The drill bit as recited in claim 28 further comprising a number of legs extending away from the body, and a number of cones rotatably attached to the legs, wherein the number of cutting elements are attached to one or more of the cones, and wherein the polycrystalline diamond construction forms at least part of a working surface of the cutting element.
 31. The drill bit as recited in claim 28 wherein the Pd comprises from 0.01 to 40 percent by weight of the total sintering agent.
 32. The drill bit as recited in claim 28 wherein the sintering is conducted at a pressure of greater than about 70 Kbar.
 33. The drill bit as recited in claim 28 wherein the sintering is conducted at a temperature of greater than about 1600° C.
 34. The drill bit as recited in claim 28 wherein the sintering agent additionally comprises one or more material selected from the group consisting of Sn, P, B, and mixtures thereof.
 35. The drill bit as recited in claim 28 wherein the sintering agent additional comprises a tungsten material.
 36. The drill bit as recited in claim 28 wherein the substrate is a cermet material comprising a Group VIII element of the Periodic table, and wherein the cutting element further comprises an intermediate layer interposed between the substrate and the polycrystalline diamond body that is formed from a material that is substantially free of Group VIII elements of the Periodic table.
 37. The drill bit as recited in claim 28 wherein the substrate is a cermet material that is substantially free from Group VIII elements of the Periodic table.
 38. The drill bit as recited in claim 28 wherein during the step of graphitizing, less than about 10 percent by volume of diamond grains in the diamond powder are graphitized.
 39. The drill bit as recited in claim 28 wherein during the step of graphitization, less than about 5 atomic layers of graphite are formed on diamond grains in the diamond powder.
 40. An earth boring drill bit comprising: a body having a number of cutting attached thereto, one or more of the cutting elements comprising a polycrystalline diamond construction comprising: a polycrystalline diamond body comprising a plurality of bonded-together diamond crystals; and a substrate attached to the polycrystalline diamond body, wherein the substrate is formed from a material selected from the group consisting of ceramics, metals, cermets, and combinations thereof; wherein the polycrystalline diamond construction is prepared by the process of: graphitizing part or all of a precursor diamond powder used to form the polycrystalline diamond body; combining the graphitized diamond powder with a sintering aid comprising a compound having one or more elements selected from the group consisting of Fe, Co, Ni, Mn, Ti, TiO₂, Si, Alkali earth metals, Alkaline earth metals, rare earth elements, and O, wherein the compound is selected from the group consisting of silicates, titanates, and oxides, and wherein the diamond powder and the sintering aid is disposed within a container that is sealed off from the atmosphere; sintering the diamond powder and sintering aid under high pressure conditions of greater than about 70 Kbar, and under high temperature conditions to form the polycrystalline diamond body; and attaching the polycrystalline diamond body to the substrate.
 41. The drill bit as recited in claim 40 wherein the body includes one or more blades projecting outwardly therefrom, and the number of cutting elements are attached to the one or more blades, and wherein the polycrystalline diamond construction forms at least part of a working surface of the cutting element.
 42. The drill bit as recited in claim 40 further comprising a number of legs extending away from the body, and a number of cones rotatably attached to the legs, wherein the number of cutting elements are attached to one or more of the cones, and wherein the polycrystalline diamond construction forms at least part of a working surface of the cutting element.
 43. The drill bit as recited in claim 40 wherein the compound is a titanate of a metal selected from the group consisting of Fe, Co, Ni, and Mn.
 44. The drill bit as recited in claim 40 wherein the compound is a titanate of one or more materials selected from the group consisting of Ti, alkali metals, alkaline earth metals, and O.
 45. The drill bit as recited in claim 40 wherein the compound is a titanate of one or more materials selected from the group consisting of Ti, rare earth elements, and O.
 46. The drill bit as recited in claim 40 wherein the compound is a composite oxide or solid solution of an oxide of one or more materials selected from the group consisting of Fe, Co, Ni, Mn, and TiO₂.
 47. The drill bit as recited in claim 40 wherein the compound is a composite oxide or solid solution of an oxide of one or more materials selected from the group consisting of TiO₂, alkali metals, and alkaline earth metals.
 48. The drill bit as recited in claim 40 wherein the compound is a composite oxide or solid solution of an oxide of one or more materials selected from the group consisting of SiO₂, and alkaline earth metals.
 49. The drill bit as recited in claim 40 wherein the compound is a composite oxide or solid solution of an oxide of one or more materials selected from the group consisting of SiO₂, and rare earth elements.
 50. The drill bit as recited in claim 40 wherein the compound is a composite oxide or solid solution of an oxide of one or more materials selected from the group consisting of SiO₂, and TiO₂.
 51. The drill bit as recited in claim 40 wherein the compound is a silicate of one or more materials selected from the group consisting of alkaline earth elements, and rare earth elements.
 52. The drill bit as recited in claim 40 wherein the substrate is a cermet material comprising a Group VIII element of the Periodic table, and wherein the cutting element further comprises an intermediate layer interposed between the substrate and the polycrystalline diamond body that is formed from a material that is substantially free of a Group VIII element of the Periodic table.
 53. The drill bit as recited in claim 40 wherein the substrate is carbide material that is substantially free of a Group VIII element of the Periodic table.
 54. The drill bit as recited in claim 40 wherein during the step of graphitizing, less than about 10 percent by volume of diamond grains in the diamond powder are graphitized.
 55. The drill bit as recited in claim 40 wherein during the step of graphitization, less than about 5 atomic layers of graphite are formed on diamond grains in the diamond powder. 